The present invention pertains to hearing aids. More particularly, the present invention pertains to flexible circuit board assemblies for use in hearing aids.
The modem trend in the design and implementation of hearing devices is focusing to a large extent on reducing the physical size of the hearing device. Miniaturization of hearing device components is becoming increasingly feasible with rapid technological advances in the fields of power supplies, sound processing electronics and micro-mechanics. The demand for smaller and less conspicuous hearing devices continues to increase as a larger portion of our population ages and faces hearing loss. Those who face hearing loss also encounter the accompanying desire to avoid the stigma and self consciousness associated with this condition. As a result, smaller hearing devices, which are cosmetically less visible, but more sophisticated, are increasingly sought after.
Hearing device technology has progressed rapidly in recent years. First generation hearing devices were primarily of the Behind-The-Ear (BTE) type, where an externally mounted device was connected by an acoustic tube to a molded shell placed within the ear. With the advancement of component miniaturization, modem hearing devices rarely use this Behind-The-Ear technique, focusing primarily on one of several forms of an In-The-Canal hearing device. Three main types of In-The-Canal hearing devices are routinely offered by audiologists and physicians. In-The-Ear (ITE) devices rest primarily in the concha of the ear and have the disadvantages of being fairly conspicuous to a bystander and relatively bulky and uncomfortable to wear. Smaller In-The-Canal (ITC) devices fit partially in the concha and partially in the ear canal and are less visible but still leave a substantial portion of the hearing device exposed. Recently, Completely-In-The-Canal (CIC) hearing devices have come into greater use. As the name implicates, these devices fit deep within the ear canal and are essentially hidden from view from the outside.
In addition to the obvious cosmetic advantages these types of in-the-canal devices provide, they also have several performance advantages that larger, externally mounted devices do not offer. Placing the hearing device deep within the ear canal and close to the tympanic membrane (ear drum) improves the frequency response of the device, reduces distortion due to jaw extrusion, reduces the occurrence of occlusion effects and improves overall sound fidelity. Earlier generation hearing devices function primarily by sound amplification and are typically not altered to user""s particular hearing impairment. Modern electronics improvements allow specific sound processing schemes to be incorporated into the hearing device. Similarly, custom programming can be incorporated into the hearing device circuitry allowing a truly custom device for any particular user.
The shape and structure (morphology) of the ear canal varies from person to person. However, certain characteristics are common to all individuals. When viewed in the transverse plane, the path of the ear canal is extremely irregular, having several sharp bends and curves. The overall cross section of the ear canal generally constricts as you move deeper into the ear canal. It is these inherent structural characteristics that create problems for the acoustic scientist and the hearing device designer.
For general discussion purposes, the ear canal can be broken into three main segments. The external and medial segments are both surrounded by a relatively soft cartilaginous tissue. The external segment is largely visible from the outside and represents the largest cavity of the ear canal. The innermost segment of the ear canal, closest to the tympanic membrane, is surrounded by a denser bony material and is covered with only a thin layer of soft tissue. The presence of this bony material allows for little expansion to occur in this region compared with the cartilaginous regions of the ear canal. In addition to being surrounded by cartilage rather than bone, these areas are covered with a substantially thicker tissue layer. Since there is less cushion, pressure exerted by a hearing device on the inner bony region of the canal can lead to discomfort and/or pain, especially when a deep insertion technique is used.
Since the morphology of the ear canal varies so greatly from person to person, hearing aid manufacturers and audiologists use custom manufactured devices in order to precisely fit the dimensions of a user""s ear canal. This technique frequently requires impressions of the user""s ear canal to be taken. The resulting mold is then used to fabricate a rigid hearing device shell. This process is both expensive and time consuming and the resulting rigid device shell does not perform well during the deformations of the ear canal that occur during normal jaw movement. In order to receive a properly fit hearing device, the user typically has to make several trips to the audiologist for reshaping and resizing. Even after the best possible fit is obtained, the rigid shell rarely provides comfortable hearing enhancement at all times.
Because the resulting hearing aid device shell is typically formed from a hard acrylic material, discomfort to the user is increased when worn for extended periods of time. The inability of the hard shell to conform to normal ear canal deformations can cause it to become easily dislodged from its proper position. Consequently, the quality of the hearing enhancement suffers. Furthermore, due to the added manufacturing costs, it is desirable to utilize a hearing device that is at least partially formed from an off-the-shelf or pre-formed component readily available to the audiologist or physician.
While the performance of CIC hearing devices are generally superior to other larger and less sophisticated devices, several problems remain. Complications typically arise due to the small size of CIC hearing devices and the depth that they are inserted into a user""s ear canal.
Because a CIC hearing device forms an essentially air tight seal between the tip of the hearing device and the wall of the ear canal, discomfort to a user is common. This acoustic seal prevents the equalization of pressure between the internal chamber formed between the tympanic membrane and the hearing device, and the outside environment. Due to the sensitivity of the tympanic membrane, even small pressure differentials can cause severe discomfort. Additionally, since the acoustic seal is formed by pressure exerted by the hearing device, this can also lead to discomfort.
Due to their small size and positioning within the ear canal, CIC hearing devices can cause handling problems, making insertion and removal by a user difficult and cumbersome, and can often lead to damage to the hearing device. In the larger, BTE, or ITC hearing devices, the size of the device usually makes it unnecessary to incorporate a retrieval mechanism into its structure, i.e., the wearer normally will not have any difficulty grasping the device in order to remove it. But in smaller hearing devices, such as a CIC device, retrieval cords and other extraction tools become a necessary addition in order to allow for easy and safe removal by the user.
Manufacturing problems may also arise when dealing with CIC hearing devices. The increased complexity of the sound processing electronics and the frequent need to fit all working components into a single housing, causes physical layout problems for the designer and manufacturer. The need to combine various hearing device elements, i.e., integrated circuits, receiver, microphone, capacitors, wiring, etc. into a single small space ultimately adds to the complexity of the manufacturing operation and the overall cost of the device. It is desirable to simplify the layout of the hearing device components and the manufacturing process to accommodate these complex systems. Designing the hearing device to minimize manual procedures during assembly is also desired in a mass production operation.
Further adding to the complexity of known hearing devices, they are usually formatted to be either a right handed or left handed orientation, specifically formatted for a single ear canal. Known hearing devices are therefore not interchangeable. While being substantially symmetric, the ear canals of an individual are not identical and known hearing devices require specific configurations for each ear. It would be beneficial and cost effective to be able to manufacture a hearing device with a single configuration that could be safely and comfortably used in either ear canal and with a variety of users.
The quality of the microphone system that receives sound waves is also critical to the performance of the hearing device. Interference with the microphone reception due to wind or other extraneous noise can lead to a degradation of sound quality. Additionally, vibrations from within a users ear canal and skull, as well as vibrations generated by the hearing device itself can interfere with the operation of the hearing device electronics, particularly the microphone and receiver system. Known hearing devices do not adequately isolate the microphone and receiver elements within the hearing device in order to shield them from this type of interference.
Finally, it is becoming increasingly important to keep the hearing device, and particularly the internal electronics of the hearing device, shielded from extraneous electromagnetic interference. A common problem arises when using a cellular telephone while wearing a hearing device. Magnetic interference generated by the cellular telephone may interfere with the operation of the hearing device electronics and cause a deterioration in sound quality. Shielding from electromagnetic interference is best accomplished by the use of a metal enclosure. Known hearing devices have not been able to adequately utilize metal enclosures because they typically add to the size of the device. Thin walled metal hearing device shells are therefore desired, particularly in the context of a completely in-the-canal device.
U.S. Pat. No. 5,701,348, entitled xe2x80x9cArticulated Hearing Devicexe2x80x9d (xe2x80x9cthe ""348 patentxe2x80x9d), discloses a segmented hearing device with several articulating and non-contiguous parts. The hearing device disclosed in the ""348 patent includes a rigid receiver module with a surrounding acoustic seal. The device disclosed in the ""348 patent is not applicable for complex electronic hearing device systems incorporated into a CIC hearing device. The device taught by the ""348 patent does not provide for all of the hearing device components to be included in a single device housing. Additionally, manufacturing the hearing device of the ""348 patent is not conducive to automated processes and does not fully take advantage of the available space in the device housing. A large amount of manual labor is still required to assemble the hearing device of the ""348 patent.
A circuit board assembly in accordance with the present invention solves the foregoing problems by providing a substrate having a component mounting region. The component mounting regions can be folded into a desired orientation with respect to the substrate.
In one aspect, a circuit board assembly constructed in accordance with the present invention is formed from a flexible dielectric substrate comprising a flexible portion adjacent to the component mounting region. The substrate can be folded without affecting the electrical or performance characteristics of the substrate or any components mounted on the substrate.
In another aspect, a circuit board assembly constructed in accordance with the present invention comprises a substrate having a plurality of component mounting regions, wherein each of the component mounting regions can be folded into a desired orientation.
In a further aspect, a circuit board assembly constructed in accordance with the present invention includes a first component mounting region adapted to receive a hearing device microphone, a second component mounting region adapted to receive an integrated circuit and a circuit capacitor, a third component mounting region adapted to receive a contact pad, and a fourth component mounting region adapted to receive a programming pad.